This feature allows a cryptocurrency (Bitcoin is one example of this) mining script to run within your browser by borrowing your CPU power. This allows the site to generate a tiny bit extra revenue while the user running it earns some upload credits. Obviously, a more powerful CPU with more cores and higher clock speeds will be faster.

WARNING: cryptocurrency mining is very CPU intensive so if you just set everything to the max supported settings, it is likely that it will push your CPU to high temperatures, making your computer throttle itself to prevent damage. I recommend playing around with the settings first and doing 5 minute test runs. It will help if you have a CPU temp monitoring program (like CoreTemp: http://www.alcpu.com/CoreTemp/). Once you find a comfortable setting, then let it run overnight or whatever.

Requirements:

Internet Explorer is not supported.
Ad-blockers and anti-script extensions need to be disabled on AvistaZ (there's no ads or other scripts on here anyway).
Javascript needs to be enabled.
Dual-core CPU minimum.
Also, to redeem the earned upload credit, you need to have earned 20MB minimum.

FWIW, anyone with half-decent internet will earn upload faster from seeding torrents. And you need a powerful quad-core CPU at least to earn upload credit at a decent rate (my overclocked 4.5GHz i7-3770K with its 8 threads only earned 3.5MB in ~7 minutes at maximum settings ). Still, if you want to try it out, go ahead.

PS: THEY WILL USE OUR CPU FOR EARNING BITCOINS AND IN RETURNE WE EARN UPLOAD CREDITS